Quirks & Quarks·Analysis

First breathable air produced on another planet

Bob McDonald's blog: An experiment on the Mars Perseverance rover produced oxygen from carbon dioxide sucked out of the thin Martian air.

Bob McDonald's blog: An experiment on the Mars Perseverance rover produced oxygen from the thin Martian air

The Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE) instrument being installed in the Perseverance rover. (NASA/JPL-Caltech)

While the first flight of the Mars helicopter got a lot of attention this week, an experiment on the Perseverance rover quietly accomplished another first, by making oxygen out of the Martian atmosphere. 

Embedded within the body of Perseverance is a toaster-sized instrument called MOXIE (Mars Oxygen In-Situ Resource Utilization Experiment).  The instrument is a technology demonstrator that produced five grams of oxygen from the mostly carbon dioxide Martian air.

Five grams is not a lot of oxygen. It would only keep you alive for about 10 minutes, but the success of this test is a huge step toward sending humans to live on the Red Planet, and bringing them home again.

In simplest terms, Mars will kill you. The atmosphere is extremely thin, only one per cent the pressure of Earth's, and is almost entirely made of carbon dioxide with only 0.16 per cent oxygen. Compare that to the 20 per cent oxygen in the Earth's much thicker atmosphere. That means explorers from Earth will need to provide their own oxygen by either bringing it from Earth, which is hugely expensive, or making it from resources on Mars.

A portion of a panorama made up of individual images taken by the Navigation Cameras, or Navcams, aboard NASA?s Perseverance Mars rover shows the Martian landscape February 20, 2021. (NASA/JPL-Caltech/Reuters)

MOXIE drew in a sample of Martian air, then using a combination of heat and electrochemistry, split the carbon dioxide molecules apart producing oxygen and carbon monoxide. The experiment proved that the process works, so in theory larger units could supply breathable air for Martian colonists.

The advantage of a MOXIE-like  system is that it can be set up easily and start producing oxygen right away no matter what the location. But there is another source of oxygen on Mars — ice. Like Earth, Mars has ice at the polar caps, and likely has significant amounts of sub-surface ice-rich permafrost 

Breakaway animation of MOXIE instrument and its internals. (NASA/JPL)

Not only is ice a source of water but you can crack that water into hydrogen and oxygen for both breathing and rocket fuel. Those elements can be extracted from water by electrolysis, or using electricity to break water molecules into their component elements. Ice deposits at the south pole of the moon might also be a sought after resource for lunar colonists.

Having a reliable oxygen supply on Mars is a big deal because the first humans to go there will be in for the long haul. Due to orbital mechanics of Mars and Earth, the two planets orbit the sun at different speeds, with Mars taking the outside track on the elliptical course around the sun so its year is twice as long as ours. A crew must launch toward Mars when both planets are close together on the same side of the sun, but by the time they get there seven months later, the Earth will have zoomed ahead on the inside track out of reach. So they will have to wait for their home planet to circle the sun and catch up to Mars again before they can make the return journey. That could take up to a year.

Photograph taken of the Martian sky, including Earth and Venus, by the Curiosity rover (NASA/JPL)

Martian colonists will be homesteaders, like early pioneers,  living off the land as much as possible. It will be a risky existence in the cold dry desert environment. Any problems will have to be dealt with on the spot because help is millions of kilometres and many months away.

Perhaps they will occasionally look up at a small blue dot in the pink Martian sky and think about their home planet, the only one we know of where oxygen is plentiful, the only place where a person can step outside, take a deep breath and not have to wear a space suit.

As we celebrate Earth Day this week,  let's remember that while the other planets are incredibly interesting, there is literally no place like home. So go outside and breathe some oxygen. It's free on this planet.


Bob McDonald is the host of CBC Radio's award-winning weekly science program, Quirks & Quarks. He is also a science commentator for CBC News Network and CBC-TV's The National. He has received 12 honorary degrees and is an Officer of the Order of Canada.